In recent years, from the viewpoint of energy conservation, light-emitting diodes (hereinafter, referred to as “LEDs”) are used as light sources for illumination in place of fluorescent light, halogen lamps and the like. In addition, cultivation of plants and mushrooms by using artificial light is actively studied in recent years, and LEDs are used as the light sources of such artificial light. LEDs are more expensive than conventional light sources, and thus there is a demand for uniformly illuminating a larger region with less number of LEDs.
For using in a technique for uniformly illuminating a larger region with LEDs, known is a light flux controlling member which includes two incidence regions each having a plurality of projections formed thereon as illustrated in FIG. 12 and FIGS. 13A to 13E. The projection is composed of an inner inclining surface serving as an incidence surface, and an outer inclining surface serving as a total reflection surface. This light flux controlling member is capable of emitting light that is emitted from an LED, disposed at angle to a surface to be irradiated, toward a further position and more uniformly (see, for example, PTL 1).
As an illumination apparatus for cultivating plants which uses LEDs, an illumination apparatus that includes a plurality of light emitting devices is known, as illustrated in FIGS. 15A and 15B. The light emitting devices are disposed at a predetermined height from a surface to be irradiated and outside the surface to be irradiated in rows so that the light emitting devices face each other, and also disposed at angle to the surface to be irradiated (see, for example, PTL 2). In FIGS. 15A and 15B, reference signs 10, 20, 25, 30, 40 and 50 respectively indicate a cultivation shelf, a cultivation case, an opening of the cultivation case, a surface to be irradiated, a substrate and a light emitting device.